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Re: replacing CF bulbs

Lazarus Miskowski asked :

> Anyone have any advice for changing CF bulbs?
> Do they lose lumens over time like NO bulbs?  Or is it
> non-significant?  Should I just wait til they burn
> out?  What's the longest someone has had a CF bulb
> last?

Scott replied:

All (All) bulbs lose lumen output over time.  This includes all
flourescent, regular tungsten incandesent and halogen incandesent, etc.
 Filaments evaporate and coat the interior of the bulbs, available
useful mercury declines due to trace combining with trace contaminants,
phospors degrade with age and use, etc.

Manufacturer rated life spans usually mark when the filaments give out,
on average.  But hose rating use on/off cycles much more frequent than
10-12 hours.  The rating depends on the manufactuer -- contact your
vendor or the maker, if you can.

I reply:

All lamps do loose lumens over time but some are way better than others
at maintaining them. Fairly recently manufacturers discovered that you
could coat the inside of lamps with a barrier coating that helps to
prevent mercury from being absorbed into the glass wall. This greatly
improved lumen maintainance and also reduced the amount of mercury that
had to be added to a lamp.

Lamp life really has little directly to do with lumen maintainance but
generally any fluorescent lamp with a high hourly rating also has pretty
good lumen maintainance. PCs are certainly not at the top of the hourly
rating or lumen maintainance scale. More like below average when
compared to other fluorescent lamps. The top end of the scale belongs to
certain T8 extended life NO lamps on electronic ballasts. 30,000 hours
and 94% lumen maintainance after 12,000 hours. Replace every 4 years.
The bottom end of the scale is VHO T12 on magnetic ballasts. 10,000
hours and 65% lumen maintainance after 6000 hours. Replace every 6
months. I think PCs are probably just about where AH Supply puts them
at; 12-14 months depending on which lamp you have and how close you are
to your minimum light requirements. Truth in advertising; I like it. PW
could learn a thing or two from those guys about customer service.